Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <iostream>
#include <vector>
#include <queue>

using namespace std;

int dr[] = {0,1,0,-1};
int dc[] = {1,0,-1,0};

struct node {
	int row;
	int col;
	int deep;
};

int main(void) {
	int H,W;
	cin >> H >> W;

	int white = 0;
	vector< vector<bool> > grid(H+2,vector<bool>(W+2,false));
	for (int i = 0; i < H; ++i) {
		for (int j = 0; j < W; ++j) {
			char temp;
			cin >> temp;
			if (temp == '.') {
				grid[i+1][j+1] = true;
				++white;
			}
		}
	}

	int step = white+1;
	bool goal = false;
	queue<node> q;
	q.push({1,1,1});
	while (!q.empty() && !goal) {
		node now = q.front();
		q.pop();
		if (now.row == H && now.col == W) {
			step = now.deep;
			goal = true;
		}
		else {
			for (int d = 0; d < 4; ++d) {
				int nr = now.row + dr[d];
				int nc = now.col + dc[d];
				if (grid[nr][nc]) {
					q.push({nr,nc,now.deep+1});
					grid[nr][nc] = false;
				}
			}
		}
	}

	cout << white-step << endl;

	return 0;
}